A 4 K matrix ESR study of the rearrangement and fragmentation of molecular radical cations of alkyl formates and acetates: Direct evidence for a McLafferty rearrangement

A 4 K matrix ESR study shows that the molecular radical cations of isopropyl formate and acetate, produced radiolytically in halocarbon matrices at 4.2 K, undergo spontaneous rearrangement due to a selective intramolecular hydrogen shift from the tertiary CH bond in the isopropyl group to the carbonyl oxygen atom giving RC⁺(OH)OC(CH₃)₂, where R = H or CH₃. The radical cation of tert-butyl acetate undergoes further fragmentation at the ester CO bond following a similar rearrangement to give an isobutene radical cation in CFCl₃.